Effectiveness of anti-bullying school programs: A meta-analysis

• There is evidence of the effectiveness of interventions aimed at preventing bullying.
• There is a great heterogeneity in the design of such school interventions.
• Outcome measures most frequently used were frequency of bullying and victimization.
• The impact of the interventions on attitudes is weak and insignificant.

The large number of studies published in recent years aimed at evaluating the effectiveness of school-based anti-bullying programs recommends research to focus on synthesizing the evidence found in this regard.This study presents a meta-analysis of random clinical trials that assess the efficacy of 14 anti-bullying school programs. Sample size was of 30,934 adolescents aged between 7 and 16 years of whom 16,243 made up the Intervention Groups and 14,691 made up the Control Groups. Meta-analysis was conducted for each outcome measure, as well as heterogeneity analysis. Analysis of subgroups was performed when necessary, as well as analysis of publication bias.Results show moderate effect sizes for the outcome measures Bullying Frequency and Victimization Frequency, Attitudes and School Climate. Greater impact was observed in interventions of less than one school year duration, as well as those targeting children younger than 10 years. Subgroup analysis confirmed greater heterogeneity in studies evaluating complex interventions.In general, our results indicate that bullying and violence prevention programs in school settings are obtaining beneficial, albeit discrete, results in the outcome measures evaluated.